1. Field of the Invention
The present invention relates to a camera lens barrel having electrical contacts through which data from the lens are transmitted to the camera body.
2. Description of the Prior Art
Two automatic exposure control systems are available for automatic exposure control type cameras. The first automatic exposure control system is a shutter-priority system wherein an exposure time or a shutter speed is manually selected by the photographer with priority, and the size of the aperture opening is determined by the camera from the shutter speed thus selected so as to automatically provide suitable exposure. The second automatic exposure control system is an aperture-priority system wherein the aperture size is selected by the photographer, and the exposure time is automatically controlled by the camera so that, again, suitable exposure is provided using the shutter speed thus selected. For convenience in description, the first system will be referred to as "auto", and the second system will be referred to as "manual". The term "manual", as used herein, is broadly defined to also include the case where the photographer manually sets both the shutter speed and the aperture size without using the automatic exposure control of the camera.
In general, in carrying out an automatic exposure control and in displaying the shutter speed and the aperture size according to the automatic exposure, data from the lens, such as the maximum aperture size and the minimum aperture size of the lens, must be transmitted to the camera body when the exchangeable lens is coupled to the camera body. In order to satisfy this requirement, electrical contacts are provided on the confronting surfaces of the mounts of the camera body and of the photographing lens, respectively, so that data from the lens are transmitted, as electrical signals, directly to the camera body from the lens. The electrical contacts are urged to protrude slightly from the mount surfaces so that, as soon as the lens is mounted on the camera body, the necessary circuit or circuits are completed and data, such as maximum and minimum lens aperture sizes, can be transmitted to a control circuit or the like in the camera body.
However, since the electrical contacts protrude as described above, when coupling the photographing lens to the camera body, the electrical contacts of the camera body are rubbed by the electrical contacts of the lens so that the circuits are completed temporarily. As a result, power consumption occurs and the arithmetic operation of the control display may be carried out erroneously.